1. Field of the Invention
This invention relates generally to a video signal recording and/or reproducing apparatus, and more particularly to a video signal recording and/or reproducing apparatus which records and/or reproduces a video signal of one field unit in a period shorter than the original one field period.
2. Description of the Prior Art
A variety of video tape recorders (VTRs) equipped with an integral video camera have been proposed in the past. In the so-called "camera-integrated type VTRs" of the kind described above, reduction of the weight and size of the main body has been the greatest problem.
On the other hand, in VTRs for home use, a so-called "two rotary head helical scan type" has been known. FIG. 1 of the accompanying drawings shows the arrangement of the heads of VTRs of this type. In the drawing, reference numeral 1 represents a magnetic tape and reference numerals 2a and 2b represent tape guides that wind the tape 1 around the outer periphery of a rotary drum 3 in the range of angle of more than 180.degree..
Symbols HA and HB represent rotary heads, that are fitted to the rotary drum 3 with a phase difference of 180.degree. between them. They have azimuth angles different from each other. These heads HA and HB record and reproduce the video signals of one field unit while rotating by 180.degree., as is well known in the art.
In VTRs of this type, the track length of the video signal of one field unit is determined in advance by standard and the diameter of the rotary drum 3 is inevitably determined in accordance with the track length. Therefore, the drum diameter cannot be reduced and this is the problem to be solved in order to reduce the weight and size of VTRs.
On the other hand, VTRs which can reduce the drum diameter have been proposed to this date, as will be described below. FIG. 2 shows the head arrangement of the conventional VTRs having a small diameter drum. In the drawing, symbols Ha and Hb represent rotary heads having mutually different azimuth angles and each rotating once per one-field period of the video signals. The tape 1 is wound around the drum 4 over a wide angle range of more than 300.degree. and the rotary heads Ha and Hb record the video signals of the one-field unit while rotating 300.degree.. In other words, during the one-field period, a video camera, not shown, scans the picture surface (represented by dotted line Y in FIG. 3) having an aspect ratio 9:10, and a picture surface having an aspect ratio 3:4 among them represented by solid line X in FIG. 3 is recorded by the heads Ha and Hb as the effective picture surface in a 5/6-field period.
The recording timing will be explained with the timing chart of FIGS. 4(a) and 4(b). In the drawings, the video camera, not shown, scans the Y picture surface having an aspect ratio 9:10 during the period represented by symbol T in the drawings to obtain a video signal consisting of 315 continuous horizontal scanning lines as shown in FIG. 4(a).
However, it is only 5/6 in each field period that the heads Ha and Hb traces actually the tape 1. Therefore, 262.5 horizontal scanning components among 315 are picked up as shown in FIG. 4(b) and are recorded on the magnetic tape as a video signal having an aspect ratio 3:4. At this time, since the heads Ha and Hb trace alternately the magnetic tape, recording can be made by VTR having the head arrangement such as shown in FIG. 2 in the same way as VTR having the head arrangement shown in FIG. 1. However, since the heads Ha and Hb must have a slight phase difference at this time, the video signal of the first or second field must be somewhat delayed.
When recording of the video signal is made by use of the head arrangement shown in FIG. 2, the drum diameter can be reduced to 3/5 of VTR shown in FIG. 1.
In VTRs having the head arrangement shown in FIG. 2, however, reproduction of the recorded video signal cannot be made. For, even when the signal is reproduced from the tape 1 by use of the heads Ha and Hb shown in FIG. 2, continuous reproduced video signals such as shown in FIG. 4(b) cannot be obtained.
To cope with such a problem, Japanese Laid-Open patent application No. Sho 60-19372 discloses a construction which can reproduce the video signals by use of a variable delay line. In VTR disclosed in this prior art reference, the reproduced video signal (having a reproduction RF waveform such as shown in FIG. 4(b) obtained in the 5/6-field period of the one-field period is extended time-axially by use of the variable delay line in order to obtain the continuous reproduced video signal.
If reproduction becomes possible in such VTRs, a desire will naturally occur to use such VTRs also as a desk-top type. In other words, if the compact VTR using the small diameter drum can make photographing by the camera, record television programs, monitor, and so forth, it is no longer necessary to prepare two VTRs, that is, the camera-integrated type VTR and the desk-top type VTR, and this will be extremely advantageous for users in general.
However, in the heretofore known VTR of the type described above, recording of external input signals such as a television signal received by a tuner, for example, cannot be made.
In ordinary desk-top type VTRs in general, on the other hand, models capable of variable speed reproduction such as so-called "still reproduction", "slow motion reproduction", "high speed search", and the like, in addition to ordinary reproduction, have become wide spread. However, such a function of variable speed reproduction cannot be added to the camera-integrated type VTRs because the weight of VTR and the number of heads increase.